[Skylab]

That's good news about the hum.  I have never seen a pair of RCA tubes with black glass before.  I'm thinking those are not RCA made - probably National Union?  or maybe Ken-Rad?  In any case, RCA date codes can be hard to figure, but I am guessing that yours are made in the 17th week of 1956,  based on this from the RCA Date Code guide I have:
 
 
Quote:

From 1-46 to 8-56: For all tubes, the code was the last digit of the year) plus a
month indicator comprising the RMNEIh week code, quantized to 04 (Jan.), 08
(Feb.), 52 (Dec.), etc. Included is a "sales basis" code: a dash between year and month
indicated tubes sold on an adjustment basis; no dash indicates sale on an allowance-inlieu-
of-adjustment basis (i. e., renewal vs. OEM business). This scheme covers privatebrand
tubes, except where a buyer's special code applies, but not Government tubes.

 

[shiaokun]

hi, Skylab, thanks for the info. actually i only have one, not a pair. it's the same tube shot twice in different angles. cannot see thru the black glass so no way of telling the construction. the only transparent bit is the top. will post a picture later this week and hope that will help you solving the mystery. shiaokun

 

[shiaokun]

the top view of the mystery black-glass RCA 6SN7 GT. hope this will help identifying which company made this...

 

[shiaokun]

installed a Sylvania GTB. yellow label. i suppose that 'CC' is a date/facory code? came with a box. you can see the hand-written price: 2.15.

 

 

[shiaokun]

back to GE tubes. think it has been more than a year since...


this is a 'new' 5-star 6080 i got recently. it's not in the same nice cosmetic condition as last year's pair. sounds good nevertheless.

i suppose somewhere down the road i might get a tube tester...

 

[shiaokun]

switched on a 6AS7G from Chatham. the front is still the GE. no hissing.

 
listened to 'Rachmaninoff plays Rachmaninoff' from RCA, done by the Zenph Studios. the second half of the CD is the 'Binaural Stereo Version' of the first half, recorded with microphones placed on a dummy head. they claim this to be 'the ultimate headphone experience.' i think i need to listen to it a few more times to decide...
 

 

 

[cal8949]

I'm so jealous right now!!! i still haven't started tube rolling my amp after having it for 3 months but it looks like ill have some cash this weekend to buy tubes, hit me up if any of u guys got some to sell

 

[shiaokun]

switched on a 6SN7WGTA from TUNG-SOL. probably the most 'exotic' 6SN7GT in my collection.

 


i've guessed USN = U.S. Navy. what about CTL? and does 739 mean anything? production year-week?
 
it hissed a little in the beginning, but then quieted down before the first CD finished.

 

[Skylab]

CTL is the 3 letter Military code for Tung Sol.  Sylvania is CHS, RCA is CRC, Hytron was CHY, Raytheon was CRP, National Union was CNU, and GE was CG.

 

[shiaokun]

thanks!

 

[shiaokun]

this week's new combo:
Westinghouse 6080 with a date code 70-17
Raytheon 6SN7 GTB with a code C18
 


the sound is more 'forward' than the previous set-up, feeling like sitting close to the stage.

 

[Katun]

Hmm, this thread is quite interesting.
 
Tube rolling seems a bit complex though.

 

[Jo6Pak]

refresh my memory, please...
 
after not having listened to my 336i in about a year, i have a newly regenerated interest in it.  one thing i don't remember is whether or not i should keep a load connected while it warms up.  what is the recommended procedure for warm-up these days?  keep cans connected or does it make any difference (to the amplifier output stage)?
 
THANKS!
 
Also:  I'm considering moving away from the Senns and perhaps try some Beyers.  I'm specifically interested in the 600 ohm versions of either the dt-880 or 990.  Will the 336i drive them suckers?  I believe my HD650s are of the older, 300 ohm variety, but can't recall for certain.  The DV has no problem driving those...

 

[HeatFan12]

Quote:

refresh my memory, please...
 
after not having listened to my 336i in about a year, i have a newly regenerated interest in it.  one thing i don't remember is whether or not i should keep a load connected while it warms up.  what is the recommended procedure for warm-up these days?  keep cans connected or does it make any difference (to the amplifier output stage)?
 
THANKS!
 
Also:  I've considering moving away from the Senns and perhaps try some Beyers.  I'm specifically interested in the 600 ohm versions of either the dt-880 or 990.  Will the 336i drive them suckers?  I believe my HD650s are of the older, 300 ohm variety, but can't recall for certain.  The DV has no problem driving those...

Rollin', Rollin', Rollin'....

 
I always have a load on the DV when I power up, whether I'm using headphones or as a pre.
 

 

[Jo6Pak]

thanks for that.  i remember doing it routinely before, but then i recall at some point someone saying it wasn't necessary.  guess i'll continue to do it...